Yesterday I was rippin hardcore for about 2 hours on and off. Rev limiter bangin, all the works. On one of my short breaks, I noticed a medium sized rainbow beneath my bike on the ground (it was dumping rain). Upon close inspection, it became apparent that a small amount of oil had leaked out of the valve cover breather hose and onto the ground. It was a little bubbly and very warm. This has never happened before, and no, this isn't a brand new engine or anything. I haven't made any changes to the bike or its fuel in a while. I rode for a bit longer, and it did not continue to leak out oil after it was parked. I checked the oil window, and it had leaked out enough that it was down to 3/4 full. Why would that happen? Could it have overheated from me riding so hard, or did something mix in?